Currently there are many rongeurs that are adapted to cut, nibble or grip bone or tissue during surgical operations such as in spinal surgery. These instruments are configured to cut away the bone overlying the spinal cord during a laminectomy and a spinal decompression. Other uses include: in neurosurgery, to cut away the spine in the cervical area or in skull and brain surgery; in head and neck surgery, to remove bone in the areas of the nose and face.
One typical prior art rongeur is shown in U.S. Pat. No. 4,201,213 issued to Townsend. This device illustrates the basic components of such rongeurs, having a pair of cooperating, slidable cutting elements which are manually actuated by means of a pair of handles at its proximal end. A generally tubular movable cutting element includes therein a relatively fixed cutting element having a recess therein so as to define a footplate or anvil structure at its distal end. The footplate and sharp distal end of the movable cutting element cooperate to act as jaws and effectively cut bone or tissue placed therebetween. Because the blade edges on such rongeurs come into contact and rather quickly become dull through use, they have to be frequently resharpened. However, repeated resharpening after a time will cause misalignment of parts and therefore imperfect cutting. The subject prior art device includes a replaceable cutting tip in an attempt to alleviate this problem.
Another problem with rongeurs of this type results from the large forces that are generated when bone is compressed between the jaws of the rongeur. The large forces frequently cause failure of the metal of the footplate at its juncture with the axially directed fixed cutting element. In spinal surgery, a thin footplate is desired in order to be able to reach within the narrow spaces in the spinal canal. This necessity for a thin footplate exacerbates the weak footplate problem thus described.
Present rongeurs of this type also require that each bone chip produced by a cut be removed prior to the subsequent repetition. This is currently done by the surgical scrub nurse or surgeon wiping off the bone chip between each cut. This requires the surgeon to take his or her eyes off the surgical situs or working area during this cutting process, only to refocus on the situs after each bone chip has been removed. This process adds unnecessary time to the surgery. Each bone chip must be removed from the surgical field, in order to prevent obstruction or impingement on delicate structures such as the spine or brain.
One attempt to solve the chip removal problem is shown in U.S. Pat. No. 3,902,498 issued to Niederer. With this device, an elongated storage recess is formed in the inner cutting element so that bone chips from a number of cuts may be stored therein prior to being ejected from a side discharge opening. However, the storage capacity is limited. The bone chips may also be ejected into the surgical field.
Still another deficiency with the above prior art devices is that tissue in the operation situs may be damaged by reciprocation of the cutting members, since they do not have any means for shielding the tissue from their movement. Still another undesirable feature of many prior art rongeurs is that it crushes the bone chip being removed as it cuts the chip away from the bone.